The A/C system removes heat and moisture from the passenger compartment. It accomplishes this through the application of four physical principles: materials absorb heat as they change from a liquid to a gas (evaporate); materials give off heat as they change from a gas to a liquid (condense); the boiling point of a liquid varies with its pressure; and, heat always flows from hot to cold. For example, the first principle is demonstrated by wetting your hand and then blowing on it. As the water evaporates, it takes some heat with it and your hand feels cooler.
In the A/C system, the heat from the passenger compartment boils (evaporates) the refrigerant (R-12) in the evaporator, causing heat to be absorbed by the R-12. This heat is then released into the atmosphere when the R-12 is cooled and condensed into a liquid in the condensers.
Moisture is removed at the evaporator in the same way that water drops form on a cold glass. The moisture drips beneath the evaporator and onto the ground. This is the reason a water puddle may often be seen under the car when the A/C is operating.
The A/C compressor forces refrigerant through the system and at the same time pressurizes it, raising the refrigerant boiling point to force it to condense more easily. The compressor is engaged by an electro-magnetic clutch that is actuated when the A/C is turned on. The compressor clutch disengages when the temperature in the passenger compartment reaches the level set on the operating controls.
The condensers, which look like small radiators, are located in front and rear of the car. The front condenser is located below the front of the car, protected by a perforated pan. It has a separate blower, accessible through the front of the luggage compartment. The rear condenser is integral with the engine cover.
The receiver/drier, located in the left front wheel housing, removes small amounts of moisture and dirt from the system.
Two switches in the center console operate the A/C system.
The temperature control knob (left hand switch) regulates the temperature of cooling air coming from the A/C vents in the dash.
• Fully left low cooling
• Fully right full cooling
The blower switch (right hand switch) also turns on the compressor clutch.
• Position I no cooling, blower off
• Position II to llll... .A/C on, increasing blower speed
Vents. Air is drawn in from the passenger footwell and blown through the air conditioner evaporator where it is cooled. Air conditioned air is then emitted from the center and side dash vents.
For maximum cooling, the console A/C control switches should be turned to the extreme right.
For information on A/C system component replacement, see 870 Air Conditioner.
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